multiple class attributes in custom styles

hi. whilst i know that multiple styles work in the custom styles XML defined drop down, is there a way to make custom class (atrribute) options concat. For example

<Style name="Image right element="img">
<Attribute name="class" value="image-right" />
</Style>
<Style name="no borderelement="img">
<Attribute name="class" value="noborder" />
</Style>

<img class="image-right noborder" src="myimag.gif" />

I have a horrid feeling you are going to say no can't be done. Which would be a real shame.

Thanks all in advance.

Bassmo / Jon